1. Field of the Invention
The present invention relates to printer apparatus in which a printing operation is performed by winding a paper sheet around a platen roller, and more particularly, to thermal sublimation-type printers.
2. Description of Related Art
FIG. 18 is a schematic side view of a portion of a conventional printer apparatus. (See Japanese Laid-Open Pat. App. Pub. No. 2001-88396.) This apparatus comprises a cartridge 34 disposed detachably/reattachably above a platen roller 2 around which a paper sheet S winds. Provided on one end of the platen roller 2 is a sandwiching member 35 for sandwiching the paper sheet S. The circumference of the platen roller 2 is slightly longer than the length of the paper sheet S.
A pair of winding shafts 36, 36 is disposed inside the cartridge 34, and an ink sheet 33 is suspended between the winding shafts 36, 36.
FIG. 19 is an oblique view illustrating the winding shafts 36, 36. On the ink sheet 33, three colors of ink, yellow (Y), magenta (M), and cyan (C) are coated separately along the winding direction. Above the ink sheet 33, a thermal head 31 for heating the ink sheet 33 is arranged so that it can freely goes up and down. The thermal head 31 is connected to an image processing circuit 37, and respective image information corresponding to respective colors, yellow, magenta, and cyan, is sent from the image processing circuit 37 to the thermal head 31.
In printing, the platen roller 2, sandwiching a paper sheet S with the sandwiching member 35, is rotated so that the thermal head 31 opposes a position on the paper sheet S that is to be recorded first. The winding shafts 36, 36 are rotated so that the thermal head 31 is drawn near to the first position for yellow, and the thermal head 31 is heated.
The image information corresponding to yellow is sent first to the thermal head 31. The thermal head 31 heats the ink sheet 33, causing yellow ink thereon to sublimate. With rotating the winding shafts 36, 36 and the platen roller 2 in a direction such that the ink sheet 33 is fed, the yellow component of the image information is printed on the paper sheet S. Upon completing the printing operation for yellow component, the thermal head 31 is separated from the platen roller 2. The platen roller 2 rotates, and the paper sheet S returns to the original position. Next, image information corresponding to magenta is sent to the thermal head 31, and the winding shafts 36, 36 and the platen roller 2 are rotated to print the image information of the magenta component on the paper sheet S. Likewise, image information corresponding to cyan is printed on the paper sheet S in a similar manner. Upon completing the printing operation, the thermal head 31 is separated from the platen roller 2, and the platen roller 2 is rotated to eject the paper sheet S.
In the above-described configuration, however, it is necessary to provide a cam and a link mechanism (not shown) for parting the sandwiching member 35 away from the platen roller 2. This creates a problem in that the size of the apparatus tends to increase.